PM6686 STMicroelectronics, PM6686 Datasheet - Page 30

• Manufacturer Part Number: PM6686
• Description: Dual Step-down Controller With Adjustable Voltages, Adjustable Ldo And Auxiliary Charge Pump Controller For Notebook
• Manufacturer: STMicroelectronics

Device description
8.1.6
30/50
Figure 49. Inductor current and output voltage in NA SKIP mode
Gate drivers and logic supply
The integrated high-current drivers allow the use of different power MOSFET.
high-side driver is supplied with a bootstrap circuit with an integrated bootstrap diode. The
BOOT and the PHASE pins work respectively as supply and return rails for the HS driver.
The PVCC pin is the input for the supply of the low-side driver and PGND is the pin used as
return rail.
The PM6686 implements an anti-cross conduction protection which prevents high-side and
low-side MOSFET from being on at the same time.
The power dissipation of each driver can be calculated as:
Equation 5
Where V
The power dissipated by the drivers can be reduced lowering the sections switching
frequencies and mounting MOSFET with smaller Q
VCC pin is the input voltage rail to supply the internal logic circuit. This pin is connected
internally with a resistor to PVCC. As usual analog supply should be divided by the power
supply with a low pass filter to reduce the noise for the analog supply of the logic. Being the
resistor integrated it is enough to put a decoupling capacitor near VCC pin to realize the
filter with a components count reduction.
Inductor
current
Output
Vreg
PVCC
T
is the voltage applied to PVCC pin (+5 V) and f
ON
T
OFF
T
Doc ID 15281 Rev 4
MA X
T
IDLE
P
DISS
=
V
PVCC
⋅
Q
G
G
.
⋅
f
sw
SW
is the switching frequency.
PM6686
t